Wave transmission control



March 12, 1929. 1. G. WILSON 1,704,850

WAVE TRANSMISSION CONTROL Original Filed May 30, 1924 .3 Sheets-Sheet l A M k [IUTPUT B ENERGY ENERGY I; 1 A l Myer/far: Ira & W/Zsm 5 Sheets-Sheet I. G. WILSON WAVE TRANSMISSION CONTROL Original Filed May 30, 1924 ruk 1 B 5 HM: H: Ell 1. T V. a W m H: M fi m E 0 WW 0 m mm mm W M O w m g L. m f? March 12, 1929.

Ira & W/750/1 by W. j'

March 12, 1929. l. G. WILSON WAVE TRANSMISSION CONTROL Original Filed May 50, 1924 5 Sheets-Sheet OUTPUT ENERGY I I III fly! RADIO TRANSMITTING STATION mpg ENERGY cum; may

Ar an/0r: Ira d M/son y L RADIO RECEIVING STATION AMPLIFIER- DETECTOR Patented Mar. 12, 1929. v

UNITED STATE S g-PATENT OFF I C E IRA G. WILSON, OF BROOKLYN, NEW YORK. ASSIGNOB TO WESTERN ELECTRIC COM,-

PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 01 NEW YORK.

WAVE TRANSMISSION CONTROL.

Application filed May 30, 1924, Serial No. 716,841. Renewed September 28, 1928.

This invention relates to wave transmission systems and particularly to the control of the energy level of transmission in such systems.

An object of the invention is to provide 5 methods of and means for effectively transmitting energy of a wide range of volumes, such as is obtained in connection with public address and broadcasting programs, over a system having a limited volume range ca pacity, for example, a telephone toll line or a radio signaling system.

In any broadcasting or public address system, the power output of the transmitter varies, of course, with the intensity of the impressed sound. For a very weak input of sound energy, the electrical energy level is likely to be so low that considerable noise and cross-talk trouble may be experienced. For very large inputs of sound energy, there is danger of both cross-talking into other circuits and of overloading the repeaters, if the circuit is so equipped.

One method of dealing with this problem now in use employs at the transmitting end of the circuit a volume indicator, which gives a monitoring operator a visual indication of the amount of power in the circuit. The op erator makes adjustments in the microphone amplifier circuits so that the volume is maintained just within the necessary limits. If the sound input and, therefore, the electrical energy is too small, networks are adjusted to bring the energy level up to the lower limit; if the sound input is excessive, a loss is inserted to bring the energy level within the load limits of the system. These changes are made for cyclic changes in input, but not for instantaneous or momentary variations. It is obvious from the description that these somewhat arbitrary changes in volume are inherently unsatisfactory from a quality standpoint and that they represent a form of dis tortion. The amount of this distortion depends on the operators knowledge of the program and on his personal preferences. If he varies the networks in the wrong direction, there is no possibility in the present systems I of overcoming the resulting distortion.

In accordance with the present invention, methods and arrangements are provided whereby when adjustments are made at the input of the system to bring the volume of energy within the capacity of the system, opposite changes are made at theoutput of the system for compensation. Then, at points in the system of limited volume of energy capacity beyond the second volume of energy change, the volume range will be in general very nearly the same as at the input of the system.

Two general methods are provided by the invention for accomplishing the desired results. Either method will makedesired changes at the output end of the system when a change is made at the input end. Both methods use some type of variable network to control the energy delivered to the circuit of llmited volume range capacity.

According to the first general method, means are provided so that when an operator makes adjustments in a network at the input end to control the Volume of energy input to the system, indications of these adjustments are transmitted to the output end, and means are provided for adjusting the networks at the output end in accordance with these indications. This may be accomplished by.

(a) A \Vheatstone bridge arrangement; a network at the input end, which is variable in accordance with changes made in the network controlling the volume input, and an auxiliary line form one arm of the bridge and a network at the output end'another arm, a galvanometer at the output end giving an indication of the magnitude and direction of the unbalance in the bridge due to changes made in the input network. The adjustment in the network of the Wheatstone bridge at the output end corresponding to the galvanometer indication can be made to balance the bridge which will cause the necessary opposite changes to be made in the volume of energy delivered at the output of the system.

(b) A system of relays at the input end adapted for sending-polarized pulses corresponding to manual changes in the network at that end to operate relays at the output end for making automatic adjustments in the output network in the opposite direction.

, (c) A modification of (5) whereby a single frequency orv two frequencies are used instead of the pulsing system for controlling the relay system at the output end, tuned circuts giving the necessary selective control.

The second general method dispenses with the monitoring operator, and automatic control is obtained at both ends of the circuit of limited volume range capacity. This may be accomplished by an arrangement whereby a portion of the energy is used to controlanauxiliary circuit in such a way that it tends to maintain a constant input both to the circuit of limited range and itself. The circuit is designed'so that it inserts losses or gains of the same magnitude but opposite in sign at the two ends. The quality should then be nearly perfect in regard to the volume distortion for which the circuit is designed to compensate.

The invention may be also applied to radio signaling systems, particularly where small radio transmitting stations are used to transmit the signals to rebroadcasting stations. In such systems, an operator at the input end makes adjustments in a variable network to control the input energy in accordance with fluctuations in volume received so that the transmitting apparatus will not be overloaded and the output distorted. According to the invention, when changes are made in the network at the input of the radio transmitting station to bring the energy level within the capacity of that station, indications are transmitted which automatically cause opposite changes to be made in networks at the radio receiving station. A relay system at the radio transmitting station is used which is adapted for sending out pulses of one or the other of two control frequencies corresponding to the direction of the changes in the network at that station. These pulses of the control frequencies are used for modulating the carrier wave transmitted. Two tuned circuits at the radio receiving station, each selective to one of the modulating frequencies. are )rovided to control a pulsing receiving re ay system for making the desired opposite changes in the network at that sta tion. The circuits are arranged so that the direction of the changes in the network at the radio receiving station depends on which tuned circuit operates the pulsing receiving relay system, and therefore, upon which control frequency modulates the carrier wave at the transmitting station.

The various features and objects of the invention generally described above will be clear from the following detailed description of typical applications of the invention to particular systems as shown in the accompanying drawings:

In the drawing, Fig. 1 shows the invention applied to a circuit of limited volume of energy range capacity, means being provided for varying the energy level at the output of the circuit corresponding to changes made in the energy level at the input of the circuit. Figs. 2, 3, 4 and 5 showmodifications of the arrangement shown in Fig. 1. Fig. 6 shows' the invention applied to a radio signaling system. Like parts throughout the several drawings bear like reference characters.

Referring to Fig. 1, a circuit of limited volume of energy capacity L having an input station A and an output station B is shown.

Variable networks C and D for varying the volume of energy at the input and output, respectively, of circuit L are shown connected across that circuit. An auxiliary circuit comprises the variable networks E and F connected by the control line 6. This control line 6 may be a separate pair of wires between the variable network D is connected mechanically to the movable arm of the variable network F, so that changes in the adjustment of network F will cause corresponding changes in the adjustment of network D. The variable network E and the control line 6 form one arm of a iVheatstone bridge and the variable network F another. The resistances 7 and 8 form the other two arms of the bridge. A source of current 9 is connected between the points 10 and 11 of the bridge, and the galvanorneter 12 between the points 13 and I l of the bridge.

The operation of the circuit of Fig. 1 will now be described. The circuits are arranged initially so that when the volume of energy input received b circuit L is within the volume limits of t at circuit, the variable networks C, D, E and F are set on definite steps preferably near the average so that an equal range can be obtained on either side of the selected step on each network. Preferably, the bridge should be balanced under this condition so that no readin will be obtained on the galvanometer. If the volume of energy input is outside the range of circuit L, adj ustments are manually made in the variable net work C by moving the movable arm 20 over the contacts 1, 2 to cut in more or less of the network until the energy level is brought within the capacity of circuit L, which causes corresponding changes to be made in the adjustment of the variable network E mechanically connected to G. Then, the drop across the arm of the bridge containing network E having been changed, the bridge will be unbalanced and the galvanometer 12 will give an indication of the magnitude and direction of the unbalance, that is, an indication of the magnitude anddirection of the change in network C. The necessary adjustment in the network F can then be made to bring the bridge back to balance and at the same time to change network D correspondingly. This adjustment of networks F and D may be made manually or automatically by means such as a contact-making galvanometer controlling an auxiliary circuit, or by an automatic selfbalancing VVheatstone bridge. Then, corre sponding changes in the network D will be made to compensate for the changes in volume at the input end.

One specific system for accomplishing this is shown and described in the U. S. patent to Brewer, No. 1,356,804 issued October 26, 1920, and for a complete description of the circuits and mechanism involved this patent may be referred to. Although a simple Wheatstone bridge arrangement is shown in the figure, any other suitable type of bridge may be used.

In Fig. 2 a polarized pulse relay system is employed instead of the VVhcatstone bridge arrangement of the previous figure for male. ing the adjustment of the output network to compensate for adjustments at the input. As in the previous figure, the variable networks C and D for controlling the volume of energy at the input and output, respectively, of circuit L are shown connected across that circuit. The transmitting relay system G controlled by the variable network C is adapted for sending polarized pulses corresponding to changes made in network C over a line 17 to control a receiving relay system H which in turn makes opposite proportional adjustments in variable network D connected across the output of circuit L. Although specific relay systems are shown in Fig. 2 and the succeeding figures for controlling networks to make changes in the energy level, any relay systems which will perform the same functions as the systems shown may be used.

The operation of the system shown in Fig. 2 will now tie described. It is assumed in this and the succeeding figures that the circuits are arranged initially so that when the volume of energy input received by circuit L is within the volume limits of that circuit, the variable networks C and D are set on definite steps, preferably near the average so that an equal range can be obtained on either side of the selected step on each network. Then the movement of the arin 20 over the contacts 1, 2, etc. in either direction from the selected step of network C will cause a corresponding proportional movement of the arm 21 over similar contacts, each of which is connected to certain relays of the transmit ting relay system G. The resulting operation of these relays causes corresponding polarized pulses to be transmitted over the line 17 These polarized pulses will cause the proper relays in the H receiving relay system to function so as to make proportional adjustments in the network D in the opposite direction from the input adjustment. The operation of the relay circuits is as follows:

If we assume arm 20 on contact 3 of network C, then a circuit is closed from battery through windings of relays 3" and 3 in series in the sending circuit through arm 21 to ground, causing relays 3' and 3" to operate. Assume also six relays in the receiving relay circuit, 25, 26, 27, 28, 29 and 30 already operated by key 22, corresponding to the third step of network D. It is assumed that the networks at the transmitting and receiving ends are so arranged that a movement of the movable arm of the network at the-transmitting end from a higher numbered to a lower numbered contact will put less loss in the sending circuit and operate relays which will adjust the network at the receiving end to put more loss in the receiving circuit. If the arm 20 is moved to contact 2, putting less less in the sending circuit, a circuit is completed from battery through winding of relays 2 and 2" through arm 21 to ground, causing relays 2 and 2" to operate. Relay 3 releases and a circuit is made from battery through the winding of relay 15, the armature of 2, and the armature of 3 to ground, causing relay 15 to op crate, which closes a circuit'from negative battery through the armature of polarized relay 15-16, line 17 and windings of polarized relay 19 18 to ground, starting a negative pulse on line 17. Slow release relay 3" then releases, opening circuit for relay 15, which releases its armature disconnecting the negative battery from the line 17, making the end of the negative pulse. In the receiving circuit polarized relay 18 operated by the negative pulse puts a ground on the midpoint between relays 29 and 30 through the left-hand armatures and back contacts of relays 33 and 31, these relays all being released. Relay 30 then releases. Relay 29 does not. release since the one winding in the circuit is sufiicient to hold it operated.

At the end of the pulse relay 18 releases,'

ground is removed from the mid-point of 29 and 30 and relay 29 releases. As a result more loss is inserted by the network D, since the shunt is decreased by the closing of the contacts on the left side of relay 30. If arm 20 is moved still further to contact 1, putting still less loss at the sendin end, a circuit is completed from battery through windings of relays 1' and 1 to arm 21 to ground causing these relays to operate. Rela 2 then releases and a circuit is made rom battery through the winding of relay 15, armature of 1' and the armature of 2" to ground. Then relay 15 operates again starting a negativepulse of battery on the line 17. Slow release relay 2 then releases, opening circuit through relay 15 which releases also, making the end of the negative pulse in the transmitting circuit. In the receiving relay system H, relay 18 is operated by the pulse of positive battery and puts ground on mid-point between the relays 27 and 28 through the left hand armatures and back contacts of relays 33, 31, 29 and 27. Relay 28 then releases but relay 27, having one winding in the circuit, holds. At the end of the pulse, relay 18 releases and ground is removed from mid-point between relays 27 and 28. Relay 27 releases due to the opening of the ground by the release of relay 18. As a result more loss is inserted by the network D. I

Assume our original conditions again with the arm on contact Suppose arm 20 is moved to contact 4, putting more loss at sending end. Then relays 1 and 1 operate and relay 3 releases closing circuit through armature of relay 3 and armature of relay 1'. Relay 16 then operates starting a pulse from positive battery on the line 17. Slow release relay 3 then releases opening circuit through relay 16 which releases also, making the end of the positive pulse. In the receiving relay system ll relay 19 is operated by the positive pulse and puts ground on the mid-point between relays 31 and 32 through the armatures and operated contacts of relays 25, 27 and 29. Relay then operates since it is short-circuited. Relay 31, however, does not operate since it is short-circuited. At the end of the pulse relay 3i operates since it has no circuit to ground, and the circuit is then on the fourth stop, loss loss having been inserted at the receiving end due to the operation of relay 32.

By n'iultiplying, as shown in the figure any number of contacts may be used on the sending controls of Figs. 2, 3, 4 and 6 without increasing the number of relays necessary. The receiving circuit is also capable of extension to an number of contacts by adding a pair of re ays per contact. If available, two auxiliary circuits may be used for transmitting signals to operate the receiving relay system instead of the polarized pulse system shown in Fig. 2.

Fig. 3 shows a two-frequency arrangement for controlling the direction of the adjustment in the network at the output of the circuit of limited range, capacity. The ap paratus in Fig. 3 is identical with that in Fig. 2 except for that connected between relays and 16 of relay transmitting system G and relays 18 and 19 of the relay receiving system H. An auxiliary line 35 is used as a coin nection instead of the line '17 of the previous figure. The circuits are so arranged that the operation of relay 16, due to the movement of the arm of the variable network C to insert more less in the inputof circuit L, will connect the source of alternating current 37 having a frequency f, across the input end of circuit Similarly, the operation of relay 15, due to the movement of the arm 20 of the variable network 0 to insert less less in the input of circuit L, will connect the source of alternating current 36 having a frequency f across the inputend of the circuit 35. The amplifier detector circuits 38 and 39 connected across the output end of circuit are tuned so as to be selective to currents of frequencies 7, and f respectively. The amplifier de tector circuits 38 and 39 control the operation of the relays 18 and 1-9 respectively, in the receiving relay system D. As described in connection with the previous figure, the operation of relay 18 adjusts the output network in one direction while the operation of relay 19 adjusts the output network in the opposite direction, the adjustment being always in the opposite direction from the adjustment in the input network. If desired, the auxiliary circuit 35 may be dispensed with, the signals for making the adjustment of the output network bcing sent over circuit L, provided suitable arrangements are used for separating them from other signals at the output.

Fig. 4. shows an arrangement similar to that shown in Fig. 3, except that a single treqnency is used instead of two frequencies for control. Two auxiliary circuit-s 40 and 41 are used, and the circuit of a source of alternating current 14 having a frequency f, is arranged so that it may be connected either across circuits 40 or 41 by the operation of relay 16 or 15, respectively. Amplifier-dctector circuit 43 and 44 operable by frequency f, are connected across the output end of circuits 40 and 41 respectively, and control the operation of relays 19 and 18, respectively, in the receiving relay system H. As de scribed. in connection with Fig. 2, relays 18 and 19 control the adjustment of the output network D in the opposite direction from the adjustment of the input network 0. As in the case of the arrangement shown in Fig. 3, one of the auxiliary circuits 40 and 41 may be dispensed with, the signals for making the adjustment of the output network being sent over circuit L, provided suitable arrangements are used for separating them from other signals at the output end.

Fig. 5 shows an arrangement for automatically controlling networks at the input and output of a circuit of limited volume range capacity. As in the previous figures, a circuit L having input and output stations A and B, respectively is shown. Variable networks C and D for controlling the volume of energy at the input and output, respectively of circuit L are conncctedacross that circuit. The amplifier detector circuit 47 which is conncctcd across the input end of circuit L controls a system of relays J which controls the adjustment of the network C at the input end of circuit L, by means of the relay system K. The relay system J also transmits signals over the auxiliary line 57, for controlling the relay system M at the output end of circuit L. The relay system M controls the adjustment of the variable network D connected across the output end of circuit L. Although an amplifier detector circuit 47 is shown for controlling the adjustment of the variable networks G and D through the relay systems K and M any device which will respond directionally to, difierences in energy volume may be used for that purpose. Furthermore, although amplifier detector circuit 47 is shown bridged across circuit L it may be connected in any suitable way so that the amount of energy it receives depends on for that purpose.

The operation of the circuit of Fig. 5 will now'be described. The circuit is adjusted initially so that with a normal energy input to circuit L at the input station A, relay 48 is not operated but for an increase in the energy input it will close one contact and for a decrease in the energy input it will close the other contact. Assume that the necessary number of relays in system K are operated to adjust the network C to step 3 and that the necessary number of relays in system M are operated to adjust the network D also to step 3. These relays may be operated electrically by means of the keys 62 and 64 respectively. Assume that an increase over the normal amount of energy is received by the amplifier rectifier circuit 47 which then furnishes current so as to operate relay 48 in the plus direction and closes a circuit from battery through relay 50 and the armature of relay 48 to ground. Relay 50 then operates closing a circuit from battery through slow release relay 52 and armatures of relays 52 and 50 to ground. Relay 52 starts to operate, closing its make-beforebreak contact which closes a circuit from battery through relay 54 armature of relay 52 and armature of relay 50 to ground, and also connects lead 55 to ground through the armature of relay 50. Then relay 54 operates putting a plus battery on the auxiliary line 57 starting a positive pulse. The slow release relay 52 then releases through its own broken contact breaking the connection to ground from lead 55 and breaking the circuit of relay 54 ending the pulse of positive battery on line 57. The pulse of positive battery on lead 55 steps the relay system K to the left which changes network C so that less energy is transmitted through the circuit L. The positive pulse of battery sent over line 57 operates relay 56 for the duration of the positive pulse to the plus side putting a pulse of positive battery on lead 58 which steps relays system M to the right changing 60 "network D so that more energy is delivered to has the output station B. The stepping of relay systems K and M will continue until the volume of energy to the input of circuit L becomes normal since relay 48 is soconstructed that it will remain operated until the current it receives from the amplifier rectifier circuit 47 falls to normal. As long as relay 48 remains operated relay 50 will also remain operated, and relay 52 as soon as it releases, will complete its circuit through the armature'of relay 50 and cause a pulse of positive battery to be sent on line 57 and a pulse of positive battery on lead 55. This causes relay circuits K and M to continue to step. WVhen the relay system K has stepped far enough so that a normal amount of energy is sent out on circu it L the input to the amplifier rectifier circuit 47 will be normal and relays 48 and 50 will return to their non-operated conditions.

Similarly, if a decrease in the normal amount of energy is received by the amplifier rectifier circuit 47 then relay 48 operates in the minus direction and closes a circuit from battery through relay 49 and armature of relay 48 to ground. Relay 49 then operates closing a circuit from battery through slowrelease relay 60 and armature of relay 49 to ground. Relay 60 starts to operate closing its make-before-break contact which closes a circuit from battery through relay 61 and armature of relay 60 and armature of relay 49 to ground and also connects lead 45 to ground through the armatures of relays 60 and 49. Relay 61 operates putting negative battery on the line 57 ,starting a negative pulse. The slow-release relay 60 then releases through its own broken contact ending the pulse of ground on lead 45 and breaking the circuit of relay 61. ending the pulse of negative battery on the line 57. The pulse of negative battery on lead 45 steps the relay system K to the right changing network C so that more energy is transmitted to circuit L.- The negative pulse of battery sent over the line 57 operates relay 56 for the duration of the negative pulse to the minus side putting a pulse of negative battery on lead 65 which steps relay system M to the left changing network D so that less energy is sent to the output station B. As in the previous-case, the stepping of relay systems K and M will continue until the volume of energy to the input of circuit L becomes normal.

As in the case of Fig. 2 two auxiliary circuits, if available, may be used for transmitting signals to operate the receiving relay system instead of the polarized pulse system of Fig. 5. Also, either the two frequency system of Fig. 3 or the single frequency system of Fig. 4 may be used instead of the direct current pulsing system shown in Fig. 5.

The chain of relays J in the sending circuit of Fig. 5 may be made slow-acting to prevent hunting, and also so that only the gradual changes in volume will be compensated for rather than instantaneous surges or rests.

In Fig. 6 is shown the two-frequency control arrangement described in connection with Fig. 3' applied to a radio signaling system. Referring to the figure, a radio transmitting station having input apparatus 0 and transmitting apparatus P is used for transmitting" signals to a radio receiving station having input apparatus Q and output apparatus R. The control apparatus at the radio transmitting station comprising the variable network C, the relay transmitting system G and the two frequency control circuit 35, is the same as shown at the input station in Fig. 3 the operation of which has been described in connection with previous figures. However, the auxiliary circuit 35 instead of being connected directly to the amplifier detector tuned circuits 38 and 39 as shown in Fig. 3, are connected directly to the radio transmitting apparatus P, the pulses of the control frequencies f, and. f being used for modulating the carrier wave transmitted by that apparatus. The gain control apparatus at the radio receiving station comprising the amplifier detector tuned circuits 38 and 39, the receiving relay system H and the variable network D, is the same as the gain control apparatus shown at the output station in Fig. 3, the operation of which has also been ex plained in connection with the previous figures. However, the amplifier detector circuits 38 and39, instead of bein connected across the output end of the auxiliary circuit 35 as in Fig. 3, are connected to the radio receiving apparatus Q.

The operation of the arrangement of Fig. 6 is as follows:

The input energy received by the input apparatus O is brought within the capacity of the radio transmitting apparatus P by adjustment of the variable network C and the modified carrier wave is modulated by the pulses of the control frequencies f, and f and transmitted to the receiving apparatus Q of the radio receiving station. The tuned cireuits 18 and 19, selective to the modulation frequencies f, and f respectively, operate the receiving relay system so as to make changes in the variable network D at the radio receiving station proportional to changes in the input'network C at the radio transmitting station but opposite in direction. Therefore, the output energy at the output apparatus R of the radio receiving station will be very nearly of the same volume range as that received at the input apparatus of the radio transmitting station. Although in the figure the same radio transmitting and receiving station have been shown for transmitting and receiving the control signals and other signals, if available. separate transmitting and receiving stations may be used for the control signals. Although a simple resistance type of network has been illustrated in the accompanying drawings, any type of network. which may contain capacity and inductance as well as resistance, may be used for the purpose. Although these networks are shown in the figures as being connected across the transmitting end such as 15, 16 in Figs. 2,

3 and 4, or 61 and 54 in Fig. 5, and corresponding relays at the receiving end such as 18, 19 or 56 regardless of whether these relays are used for transmitting and receiving polarized pulses or waves of characteristic frequencies. It will be clear, therefore, that any type of auxiliary control system may be used in connection with any of the relay-control systems. For example, in place of the line 57 in Fig. 5 it would be obvious to use the line 35 of Fig. 3 together with the wave sources and amplifier detector circuits. Similarly in Fig. 6, which is the only figure specically showing radio transmission, the volume range control system may be that of one of the other figures, for examplethat of Fig. 5.

The applications of the invention above illustrated and described should be considered merelyas typical and not as limiting the invention, the scope of which is defined in the appended claims.

What is claimed is:

1. In a transmission system, a transmission medium interconnecting two stations, volume adjusting means at each station, a control switch, means operated by a change in the setting of said switch to transmit impulses to each of said stations, and means responsive to the transmitted impulses to cause simultaneous and complementary adjustments of the volume adjusting means at the two stations.

2. In a transmission system, a transmission medium interconnecting two stations, volume adjusting means at each station, a control switch, means operated by a change in the setting of said switch to transmit impulses to each of said stations, and step-bystep means responsive to the transmitted impulses to control said volume adjusting means to simultaneously efi'ect complementary stepby-step adjustments of the volume at the two stations.

3. In a transmission system, a transmission medium interconnecting two stations, volume adjusting means at each station. a control switch, means operated by a change in the setting of said switch to transmit impulses to said stations, sets of counting relays at the two stations responsive to the impulses transmitted to control said volume adjusting means to produce simultaneously complementary step-by-step adjustments of the switch, means operated by a change in the set ting of said switch to transmit impulses to each of said stations, sets of counting relays at each station, said counting relays being successively operated in one order at both stations in response to impulses resulting from adjustment of said switch in one direction and being successively operated in a reverse order in response to impulses resulting from an adjustment of said switch in the opposite direction, the operation of sald counting relays at the two stations controlling the volume adjusting means to produce simultaneously complementary step-by-step adjustments of volume at the two stations.

5. In a transmission system, a transmis sion medium interconnecting a sending station and a receiving station, volume adjusting means at each station, a switch at the sending station for controlling the volume adjusting means thereat, means responsive to the manipulation of said switch in one direction to transmit impulses of certain characteristics over said medium to said receiving station, means responsive to the manipulation of said switch in the opposite direction to transmit impulses of other characteristics over said medium to said receiving station, and a plurality of switching means at the receiving station for controlling the volume adjusting means thereat, said switching means being operated successively in one order in response to impulses of said certain characteristics received over said medium to control the volume adjusting means at said receiving station in the opposite direction to and proportionate to the corresponding volume ad ustment at the transmitting station, said switching means being operated successively in reverse order in response to the impulse of said othercharacteristicsreceivedoversaidmedium to control the volume adjusting means in the opposite direction to and proportionate to the corresponding volume adjustment at the transmitting station.

6. In a transmission system, a transmission medium interconnecting a sending station and a receiving station, volume adjusting means at each station, a switch at the sending station for controlling the volume adjusting means thereat, means responsive to the manipulation of said switch in one direction to transmit impulses of certain characteristics over said medium to said receiving station, means responsive to the manipulation of said switch in the opposite direction to transmit impulses of other characteristics over said medium to said receiving station, and a plurality of switching means at the receiving station for controlling the volume adjusting means thereat, said switching means being operated successively in one order in response to the impulses of said certain characteristics transmitted over said medium to control the volume adjusting means at said receiving station in one sense, said switching means being operated successively in reverse order in response to the impulses of other characteristics transmitted over said medium to control the volume adjusting means in another sense.

7. A system for simultaneously controlling the gain of a plurality of repeaters comprising a controlling device, a transmission medium between said controlling device and said repeaters over which impulses of dillerent characteristics may be transmitted controlled by said control device and means responsive to said impulses of different characteristics to control the gain of said repeaters. V

8. A system for simultaneously controlling the gain of a plurality of amplifiers, each of which is located at a dill'erent station, comprising a control device, a transmission medium between said control device and said different stations over which impulses of different characteristics may be transmitted controlled by said control device, a plurality of relays at each of said stations electrically responsive in one direction to one of said char acteristic impulses to increase the gain of the amplifier thereat and electrically responsive in the other direction to another of said characteristic impulses to decrease the gain of the amplifier thereat.

9. A system for simultaneously controlling the gain of plurality of repeaters located at difierent stations, comprising a control device, a transmission medium between said control device and each repeater station over which impulses may be transmitted controlled by said control device, a plurality of relays at each station, the impulses due to operation of said control device in one direction controlling over one medium the relays at one of said stations to increase the gain of the repeater thereat, and controlling over another medium the relays at another station to decrease the gain of the repeater thereat, and the impulses due to operation of said controlling device in the opposite direction controlling over said one medium the relays at said one station to decrease the gain of the repeater thereat, and controlling over said other medium the relays at said other station to increase the gain of the repeater thereat.

10. In combination, a source of energy of a wide range of volumes, a circuit of limited volume range capacity supplied with said energy, means for varying the input energy to said circuit, means controlled by said firstmentioned means for transmitting pulses to the output of said circuit, and means controlled by said pulses for changing the en; ergy output of said circuit.

11. In a wave transmission system, a source of energy of a wide range of volumes, a circuit of limited volume range capacity supe plied with said energy, means for changing the energy input to said system, means controlled by the first mentioned means for transmitting to the output of said system current pulses of certain characteristics for a change in said energy input in one direction, and pulses of different characteristics for a change in said energy input in the opposite direction, means responsive to the impulses of said certain characteristics to change the energy output of said circuit in one direction, and means responsive to the impulses of said difi'erent characteristics to change the energy output of said circuit in the opposite direction.

12. In a transmission system, a transmission medium for transmitting signals between a sending station and a receiving station, means for adjusting the volume of the signals at each station, a switch at the sending station for controlling the volume .adjusting means thereat, means responsive to the manipulation of said switch in one direction to transmit impulses over said medium to said receiving station, means responsive to the manipulation of said switch in the opposite direction to transmit other impulses over said medium to said receiving station, a plurality of switching means at the receiving station for controlling the volume adjusting means thercat, said switching means being operated successively in one order in response to the first mentioned impulses received over said medium to control the volume adjusting means at said receiving station to make an adjustment in the volume of the received signals opposite to and proportional to the correspon ing volume adjustment of the signals at the transmitting station, said switching means being operated successively in re verse order in response to said other impulses to control the volume adjusting means at said receiving station to make an adjustment in the volume of the received signals opposite to and proportional to the corresponding volume adjustment of the signals at the transmitting station.

In witness whereof, I hereunto subscribe my name this 27 day of May, A. D., 1924.

IRA G. WILSON. 

